Powder distribution system for three-dimensional printer

Abstract

The present invention relates to apparatuses for distributing build powder in powder-layer three-dimensional printers (2) and for the collection of particulates of the build powder that have become suspended in the gaseous atmosphere in the vicinity of the build platform of the three-dimensional printer. These apparatuses include recoaters (20) that are particularly useful in providing uniform distribution of fine build powder across the width of the build platform or powder bed. The present invention also includes powder-layer three-dimensional printers (2) which comprise such apparatuses for distributing build powder and/or apparatuses for collecting such suspended particulates. The improved fine powder recoater (20) uses an ultrasonic transducer (30) to move powder through a sheet screen (28). The sheet screen (28) may be presented to the powder fed onto it in a narrow dispensing slot to limit the flow rate of powder from the dispenser and to provide control over the amount of powder dispensed. The width of the slot may extend to cover the entire build box fill zone. The ultrasonic transducer (30) is preferably adapted to periodically sweep through a range of frequencies during operation. The ultrasonic vibration system may be augmented with a low frequency vibration system. The dust collection system (160) draws air from the perimeter of the build box (172) down through the deck plate (170) of the printer (2) and out of the printer's housing (164) to an external dust collector (250).

What is claimed is: 
     
       1. A powder-layer three-dimensional printer ( 2 ) comprising: a recoater ( 20 ) having a sheet screen ( 28 ) having a plurality of perforations ( 126 ) and a first side and a second side, an ultrasonic transducer ( 30 ) adapted to vibrate the sheet screen ( 28 ), and a hopper ( 26 ) adapted to provide a build powder to a first side of the sheet screen ( 28 ), wherein when the ultrasonic transducer ( 30 ) vibrates the sheet screen ( 28 ) the build powder from the hopper ( 26 ) is dispensed from the sheet screen second side via the perforations ( 126 ), a low frequency vibrator ( 32 ) adapted to apply vibrations to the hopper ( 26 ), and a vibration controller ( 262 ) in operative communication with the ultrasonic transducer ( 30 ) and the low frequency vibrator ( 32 ) and adapted to cause the ultrasonic transducer ( 30 ) and the low frequency vibrator ( 32 ) to operate at least one of simultaneously and non-simultaneously. 
     
     
       2. The powder-layer three-dimensional printer ( 2 ) of  claim 1  wherein, when the ultrasonic transducer ( 30 ) vibrates the sheet screen ( 28 ) the build powder from the hopper ( 26 ) is dispensed from the sheet screen second side via the perforations ( 126 ) as build powder pellets ( 112 ). 
     
     
       3. The powder-layer three-dimensional printer ( 2 ) of  claim 1  wherein, the hopper ( 26 ) is adapted to provide mass flow of the build powder to the sheet screen first side. 
     
     
       4. The powder-layer three-dimensional printer ( 2 ) of  claim 1  wherein, the hopper ( 26 ) comprises a lower portion ( 60 ) proximate to the sheet screen ( 28 ) and an upper portion ( 58 ), the lower and upper portions ( 64 ,  58 ) being interconnected to form a continuous reservoir. 
     
     
       5. The powder-layer three-dimensional printer ( 5 ) of  claim 1  further comprising, a sheet screen holder ( 78  &  110 ), the sheet screen holder ( 78  &  110 ) having first and second sides and an aperture extending therebetween, wherein the sheet screen ( 28 ) is attached to the sheet screen holder ( 78  &  110 ) so that at least some of the perforations ( 126 ) of the sheet screen ( 28 ) are in fluid communication with the aperture. 
     
     
       6. The powder-layer three-dimensional printer ( 2 ) of  claim 5  wherein, the sheet screen ( 28 ) is bonded to the sheet screen holder ( 78  &  110 ) by an adhesive. 
     
     
       7. The powder-layer three-dimensional printer ( 2 ) of  claim 1  wherein, the sheet screen second side is positioned at an angle of between 20 and 70 degrees to the horizontal. 
     
     
       8. The powder-layer three-dimensional printer ( 2 ) of  claim 1  wherein, the ultrasonic transducer ( 30 ) is positioned at an angle to the horizontal so as be able to apply to the sheet screen ( 28 ) a vibration having both a horizontal component and a vertical component. 
     
     
       9. The powder-layer three-dimensional printer ( 2 ) of  claim 1  wherein, the ultrasonic transducer ( 30 ) is adapted to sweep across a frequency range during its operation. 
     
     
       10. The powder-layer three-dimensional printer ( 2 ) of  claim 1  wherein, at least one of the size, shape, and distribution of the perforations ( 126 ) of the sheet screen ( 28 ) is varied to reduce any tendency the recoater ( 20 ) otherwise would have to dispense build powder non-uniformly due to local vibration variances. 
     
     
       11. The powder-layer three-dimensional printer ( 2 ) of  claim 1  wherein, at least one of the perforations ( 126 ) has a hole shape which includes at least one tine ( 154 ). 
     
     
       12. The powder-layer three-dimensional printer ( 2 ) of  claim 1  further comprising, a trolley ( 22 ) adapted to carry the recoater ( 20 ). 
     
     
       13. The powder-layer three-dimensional printer ( 2 ) of  claim 1  wherein, the recoater ( 20 ) further comprises at least one of a smoothing device ( 34 ), a drying device ( 36 ), and a curing device. 
     
     
       14. The powder-layer three-dimensional printer ( 2 ) of  claim 1  further comprising, a housing ( 164 ) enclosing a space having a gaseous atmosphere, a horizontally disposed deck ( 170 ) dividing the space into an upper section and a lower section, a build box ( 172 ) positioned proximate to the deck ( 170 ) and at least in part of the space upper section, a plurality of passageways ( 176 ) through the deck ( 170 ) located so as to surround the build box ( 172 ) and providing fluid communication between the space upper and lower sections, a plenum ( 178 ) located in the space lower section and in fluid communication with the passageways ( 176 ), an exhaust duct ( 180 ) in fluid communication with the plenum ( 178 ), and a dust collection unit ( 186 ) located outside of the housing ( 164 ) and including a controllable vacuum source ( 192 ) and a filter ( 188 ) both in fluid communication with the exhaust duct ( 180 ), wherein when the vacuum source ( 192 ) is operated at least some of the gas of the gaseous atmosphere in the space upper portion is drawn through the passageways ( 176 ) and through the filter ( 188 ). 
     
     
       15. The powder-layer three-dimensional printer ( 2 ) of  claim 14  further comprising, a shroud ( 208 ) surrounding the build box ( 172 ) and forming therebetween an annulus ( 212 ), the annulus ( 212 ) providing fluid communication between the space upper section and the passageways ( 176 ). 
     
     
       16. The powder-layer three-dimensional printer ( 2 ) of  claim 14  wherein, wherein the housing ( 164 ) has at least one vent ( 206 A) providing fluid communication between the gaseous atmosphere in the space upper section and an atmosphere outside of the housing ( 164 ).